Friday, January 21, 2011

US Milsat NROL-49 Launched

With the Moon beaming above, a United Launch Alliance Delta IV Heavy sits poised on its launch pad with a National Reconnaisance Office payload at Space Launch Complex-6. Today's launch is scheduled to blast off at 1:08 p.m. PST. The Delta IC Heavy, standing 235 feet tall, will be the largest rocket to ever launch from the West Coast of the U.S. With it's nearly 2 million pounds of thrust, the Delta IV Heavy is America's most powerful liquid fueled rocket. (Pat Corkery, United Launch Alliance)

In an email posted to SEESAT-L Ted Molzcan wrote:
Bob Christy has reported radio observations on two consecutive passes, early on Jan 21 UTC, which lead me to believe that the initial orbit is similar to that of USA 186, after its launch in Oct 2005. Here are revised elements:

163 X 1027 km
1 72001U 11020.92423331 .00988049 00000-0 77000-3 0 09
2 72001 97.9000 135.1447 0620000 185.0000 174.4842 14.90000000 08

The elements remain fairly rough, so significant time and track errors should be expected. Next step will be to raise perigee by about 100 km. My guess is that will occur within range of Diego Garcia, on Jan 22 near 19:14 UTC or 20:49 UTC.

Pre-launch Ted posted this to the SEESAT-L group regarding NROL-49:

It will launch a KeyHole imagery intelligence satellite of KH-11 lineage, which will replace a similar satellite in the standard eastern KH plane: USA 161 (01044A / 26934), launched from VAFB on a Titan 4B, in October 2001.

Accurately estimating KH orbits pre-launch is complicated by uncertainty about the planned argument of perigee of their moderately eccentric (for LEO) orbits. There are two standard KH planes, with nodes separated about 49 deg, and argument perigee separated by roughly 90 to 180 deg.

I have experimented with several different arguments of perigee, ranging from 141 deg to 244 deg, and settled on 141 deg, but its just a guess, and on past launches I have generally guessed wrong by tens of degrees.

The second stage rocket body apparently will be de-orbited on the first rev; the centre of the debris footprint is on the equator, near 152 W. I have taken that into account in guessing the argument of perigee, since the de-orbit should be roughly at apogee.

I have also guessed that the extraordinary performance of the Delta 4 Heavy will be used to insert the spacecraft into its standard ~270 km perigee, instead of the past practice (with Titan 34D and Titan 4), which was to insert into ~150 x 1000 km, and have the spacecraft raise its perigee.

I have assumed that the plane will match that of USA 161, but it could easily differ by a degree or two.

The following elements are based on launch at window-open:

272 X 1038 km
1 72001U 11020.91666667 .00000000 00000-0 00000-0 0 04
2 72001 97.9000 135.1374 0545000 140.9173 179.6287 14.71000000 03

In the event the launch is delayed, I will post an update.

Prediction time error during the first few hours is likely to be several minutes. Track error could be quite large, due to the uncertainty in argument of perigee.

If the argument of perigee is correct, then southern hemisphere observers around 35 S or so, will have middle of the night visibility. But if I am way off - for example, should it match the argument of perigee of USA 161, then the orbit will be in eclipse.

There is an interesting article posted to the about how the launch patch associated with NROL-49 gives a hint to its mission (Keyhole Recon). See that article at